In recent years, various technologies for high recording capacity magnetic disk devices (for example, HDDs) have been developed. One such technology is magnetic disk devices that write data via shingled write magnetic recording (SMR). When a magnetic disk device writes data on disk via a shingled write magnetic recording, the magnetic disk device writes the current track to overlap parts of a track (hereinafter simply referred to as adjacent tracks) that is written immediately before the current track. Magnetic disk devices can further improve track densities (track per inch (TPI)) of disks by writing data via shingled write magnetic recording rather than via conventional magnetic recording.
Magnetic disk devices control the widths of remaining adjacent tracks, that is, read track widths that do not include overwritten regions of the adjacent tracks, by controlling the width of the regions overwritten on the adjacent tracks. Therefore, magnetic disk devices can control read track widths, for example, with a function (e.g., adaptive track center (ATC) function) that sets target trajectories of current tracks based on positioning error information of adjacent tracks in which data is written.
Magnetic disk devices write current tracks based on adjacent tracks, for example, via the ATC function. In a sector in which data writing starts (hereinafter referred to as a starting sector) in an immediately previously written adjacent track, the data writing may possibly end in the same adjacent track. In addition, the starting sector may possibly deviate from a sector adjacent to the starting sector (hereinafter referred to as an ending sector) in a radial direction of the disk. For example, when a starting sector deviates from an ending sector in a direction in which a subsequent track of a current track is to be written (hereinafter referred to as a forward direction) in a radial direction of the disk, a magnetic disk device writes the current track based on an adjacent track by the ATC function. In this case, a read track width of a region near the starting sector of the adjacent track can be compressed in the radial direction.